1. Field of the Invention
This invention relates to an assembly providing low resistance connections between electrical conductors and more particularly to an improved assembly for establishing a low resistance connection between conductors adapted to carry high current.
2. Description of the Prior Art
Connections between conductors carrying high currents such as 400 amps and above are subject to blow apart forces due to constricting current paths and opposing large magnetic fields.
Various attempts have been made to improve such connections and reduce resistance as well as blow apart forces. One approach in avoiding the blow apart forces at the connection utilizes a jawlike assembly with one end of the assembly secured to opposite sides of a bus bar and the other end projecting forwardly to receive therebetween another bus bar. The jaw members are biased together by heavy springs to hold them tightly against the connected bus bars and to resist the blow apart forces. The contact surfaces of each jaw member at the point of contact with each bus bar may be rounded to make the contact angle of current flow less acute which will tend to lessen blow apart forces. However, portions of such connecting jaws are still substantially parallel to both the source-side and load side bus bars and in relatively close proximity so magnetic fields of current paths in such connecting jaws and parallel bus bars still create substantial blow apart force. The aforementioned arrangement is also quite expensive, and imperfections in the engaged surfaces give rise to poor or high resistance contact and heating effects.
Arrangements to secure multiple current paths between associated conductors have used helical or coil springs. The turns of the springs provide a multiplicity of engaged surfaces acting in parallel which are free to adjust themselves independently to make good contact. This approach, as set out in British Pat. No. 29,822, uses a hard drawn copper or phosphor bronze helical coil with the turns set at an angle of 60.degree. to 80.degree. from the axis of the helix to the points of engagement or contact. This angle can provide high resistance to insertion or connecting forces, and phosphor bronze is inherently a high electrical resistance material with conductivity usually in the neighborhood of 18% of that of copper.
Copper on the other hand, while providing low resistivity does not generally retain its resiliency in high heat environments, such as that occurring in high current connections adapted to carry 400 amps or more. Temperatures in such environments may be maintained at 100.degree. C. and may reach a maximum transient temperature of 150.degree. C. for a 30 cps current.
It has therefore not been previously proposed to utilize a coil spring to establish connections between conductors adapted to carry currents of 400 amps or more.